Conventionally, various types of step-up/down regulator circuits have been disclosed and suggested that step up or down an input voltage to generate a desired output voltage (see, for example, Patent Publication 1).
FIG. 6 is a circuit diagram showing a conventional example of a step-up/down regulator circuit. As shown in the figure, the conventional step-up/down regulator circuit includes a switch control circuit a1, a step-down switch a2, an inductor a3, diodes a4 and a5, a smoothing capacitor a6, and a step-up switch a7, and is so configured as to step up or down an input voltage Vin from a direct-current power supply a8 to generate a desired output voltage Vout and then feed it to a load 9.
More specifically, in the step-up/down regulator circuit configured as described above, the switch control circuit a1 monitors the output voltage Vout. When a step-up operation is needed, the switch control circuit a1 turns on and off the step-up switch a7 so as to step up the output voltage Vout to a desired value. During the step-up operation, the step-down switch a2 is kept on. On the other hand, when a step-down operation is needed, the switch control circuit a1 turns on and off the step-down switch a2 so as to step down the output voltage Vout to a desired value. During the step-down operation, the step-up switch a7 is kept off.
Incidentally, other than the step-up/down regulator circuit configured as described above, there have also been known step-up/down regulator circuits called, among others, Cuk circuit, Zeta circuit, SEPIC circuit (see FIGS. 7 (a) to 7(c)).
Patent Publication 1 J P-A-2003-180072